The proposed research is to study the effects of steroid hormones on the differentiation of embryonic sex organ. Female chick Mullerian ducts will be used as a model system to investigate their biochemical and morphological responses to the sex steroids. Initially, the "hormonal environment" of the female chick embryonic sex organ will be studied by radioimmunoassay detection of estrogen and testosterone concentration in the plasma and the Mullerian duct of the embryo. The role of testosterone on the regulation of female embryonic sex organ differentiation will be studied. The nature of testosterone translocation from the cytoplasm to the nucleus in the Mullerian duct cell will be studied by administering various concentrations of testosterone in vivo. The testosterone binding sites in the nucleus will be studied by hormone exchange assay. In the absence of exogenous hormone, the biochemical activities, e.g., steroid binding sites, RNA chain initiation sites, and the enzymatic activity in the normal differentiating Mullerian ducts will be measured. After the in vivo administration of estrogen, estrogen antagonists, or testosterone, its influence on the biochemical activities of the developing left Mullerian duct will be studied. The protecting effects of estrogen on the retention of right Mullerian duct will be investigated. Specific attentions are focused on the timing of the right duct response to the estrogen for its protection, and the biochemical and morphological states of the retented right duct. Histological survey will be applied to investigate the morphological change in the Mullerian ducts during normal differentiation, and during the influence of steroid hormones. The observed changes of genomic activity and structure in chromatin during differentiation will continue to be investigated. The techniques of reconstitution of the chromatin protein component and the addition of estrogen-receptor complex to the chromatin for in vivo template assay will serve as the keys toward the understanding of where in the chromatin the changes reside.